Shiimi eventually began working for the Bank of Namibia, initially holding positions such as Head of Research and Senior Manager Banking Supervisor. He later headed the Financial Intelligence Center and several other departments of the bank. Shiimi was appointed as governor of the Bank of Namibia by PresidentHifikepunye Pohamba (1935–) on March 25, 2010, following the resignation of former governor Tom Alweendo.

In 2012, the Bank of Namibia unveiled a new series of Namibian banknotes. These notes bear the Shiimi's signature on the obverse.